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Sharks are pretty amazing creatures, as I pointed out yesterday. But since humans tend not to respect these animals — whether out of fear or other feelings — we kill a lot of them. Just take a look at the infographic below. The image, though, which has been making the rounds on the internet lately, might be off, at least a little. That’s because a team led by the Institut de recherche pour le développement in France just estimated the number of silky sharks (above) killed by fish aggregating devices set to catch tuna, and the numbers are shocking. Their study appears in Frontiers in Ecology and the Environment.

Fish aggregating devices (FADs) are huge structures of bamboo and netting that are set adrift in the open water. Tuna have a natural tendency to aggregate among floating objects, so fishermen can use satellite tracking to monitor the devices and just motor up to them and catch a whole bunch of fish.

But a lot of other critters can get tangled up in FADs, including sea turtles, marine mammals and silky sharks, a pelagic species that got its name from its silky smooth skin. In the new study, the researchers tagged and tracked 29 silky sharks off of the Seychelles and in the northern part of the Mozambique Channel. Over the next 94 days, four of the sharks became entangled in FADs.

Extrapolating from their tagged sharks, and assuming that there are some 3,750 to 7,500 active FADs in the Indian Ocean, the researchers calculate that 480,000 to 960,000 silky sharks are killed by the devices in the Indian Ocean each year, and perhaps as many as 2 million worldwide.

“FADs have been used with increasing frequency worldwide for the past 20 to 30 years,” the researchers write, “but it is only now that the unexpected impact on silky sharks in the Indian Ocean has been detected.”